<!DOCTYPE html>
<html>
<head>
	<title></title>
	<style>
		
	</style>
</head>
<body>
	<button onclick="start()">开始</button>
	<div id="box">10</div>
</body>
	<script>
		var m =10;

		function start(){

			var div = document.getElementById("box");

			m--;

			div.innerHTML = m;

			if(m<=0)
			{
				return;
			}

			t1 = setTimeout(start,1000);
		}
	</script>
</html>